/forum/forum16/topic1428/

The same topic in different forums, will remove one, the other disappears

We don't see any duplicated topics and posts. Please provide us the examples. 

Could you please provide us the admin login details to allow us to understand what the problem is? If yes please send the login details to infogvectors.com email address. 

Thanks. All done but both topics are still available.

Hi @vasiliy . Now that's a mystery.  Sorry the suggestion didn't work for you.  

Hi.

Began to appear doubles topics with the same content. 

/forum/forum21/topic1428/

/forum/forum16/topic1428/

The database entry with slug "topic1428" is only 1. And belongs forum, too, one "16"

How could appear I do not know.

Hi @vasiliy . I have noticed this phenomenon happen when an admin moves different topics, or reorganizes topics, or renames forums, etc, and changing different layouts, and "forgetting to change" the Forum Slug.   :-)

In your example,

/forum/forum21/topic1428/

/forum/forum16/topic1428/

..  

What I can suggest that you try are the steps below:

1) Try to "temporarily" change the Category (the blue bar) layout from the "threaded layout" to the "simplified layout" 

2) Go to

Forum Dashboard
Forums
On the Category Bar (the Blue Bar), select the Pencil Icon to Edit
Then under "Forum Options"
Under "Category Layout"
Select "Simplified"

Then go to the Front End of your website and see all the "topics" and "replies" that will be visible. (Because if you say there are duplicated topics, then it will appear on a Simplified layout), both the:

/forum/forum21/topic1428/

/forum/forum16/topic1428/

3) Then Go to the Front End of your "/forum/forum16/topic1428/" , and copy the exact URL to your Clipboard (press "Control A" at the URL, then "Control C" to copy the URL Forum 16's exact address to your clipboard) (Forum 16 is what you want to keep)

4) Then on the Front End of "/forum/forum21/topic1428/", click the "Tools" Icon, then select the "Merge" tab. 

5) On the "Target Topic" URL, click "Control V" (to copy the exact URL / address of Forum 16), then click Merge, like in the attached screenshot. What will happen is Forum21, will be merged with Forum16, and the Forum21 URL will be gone.  

6) After you've merged the two topics, (now with only Forum16) you can go back to your preferred Layout (whether it is Threaded, or Extended Layout) using Steps #1 and #2 above.  

Hope that helps.   Good luck and God bless you! :-)

I've asked you to check on the Published subtab. Please see the screenshot: